Sigma-term physics in the perturbative chiral quark model

Abstract

We apply the perturbative chiral quark model (PCQM) at one loop to analyse meson-baryon sigma-terms. Analytic expressions for these quantities are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our result for the piN sigma term of about 45 MeV is in good agreement with the value deduced by Gasser, Leutwyler and Sainio using dispersion-relation techniques and exploiting the chiral symmetry constraints.Comment: 19 pages, LaTeX-file, 2 Figure

Nucleon and delta sigma-terms

“…Results for the real component of σ ∆ are sensitive to the coupling constant g π∆∆ and consistent with that given in ref. [10], namely σ ∆ = (32 ± 3) MeV. On the other hand, our prediction is larger than that quoted in ref.…”

η mesons in nuclear matter

“…The value for KN sigma term has some uncertainties. The latest result is Σ KN = 312 ± 37 MeV in the perturbative chiral quark model [34]. The lattice gauge simulation gave Σ KN = 450 ± 30 MeV [35].…”

Axial form factor of the nucleon in the perturbative chiral quark model

“…However, these techniques do not always agree and lead to further ambiguities in model evaluations. Furthermore, existing Galilean projection techniques are known to lead to conflict with chiral symmetry constrains [10]. In the present manuscript we completely neglect the study of these additional model dependent effects.…”

“…The interaction of quarks with Goldstone bosons is introduced on the basis of the nonlinear σ-model [23]. The PCQM is then defined by the effective, chirally invariant Lagrangian L inv [10,11] …”